Ball grid array semiconductor devices (hereinafter referred as BGA semiconductor devices), pin grid array semiconductor devices (hereinafter referred as PGA semiconductor devices), land grid array semiconductor devices (hereinafter referred as LGA semiconductor devices), chip scale package semiconductor devices (hereinafter referred as CSP semiconductor devices), or the like in which terminals are formed in the form of grids are widely used because they can accommodate an increased number of signal lines or for other reasons.
In these semiconductor devices, in order to decrease electrical noise, in addition to first ground through-holes electrically connected to a ground layer, it has been proposed to provide a plurality of second ground through-holes electrically connected to the ground layer in a ground pattern provided in a predetermined site of a bottom surface thereof, as the semiconductor device described in JP-A-7-153869. For example, in the semiconductor device described in JP-A-7-153869, noise occurrence can be suppressed by expanding an area of the ground layer through which current effectively flows.